Structural engineer recommendation

In the course of my new Red Sea Reefer 750 (200g total) planning, I was considering adding additional flooring support. I have an evaluation and quote from an experienced contractor I use for other work, but he has never actually done this kind of work for tank support before.

Online the opinions vary quite a bit. One thing that comes up frequently is the recommendation to have a structural engineer give a formal evaluation and recommendation. It seems like planning for a tank has some considerations different from other SE jobs, so I was wondering if any of you have a recommendation for an East Bay Area SE who is familiar with tank flooring issues and is good to work with.

Do you have a crawl space? My tank is parallel to a large concrete support and has a couple large beams running perpendicular under it. However if I ever wanted to support it further I would get a few heavy duty jack posts with some concrete feet and DIY. Each jack post can hold up thousands of pounds, and there are websites showing you how to do it yourself.

If you have a more complicated scenario, you can go for a structural engineer, but it could cost you a pretty penny (for our remodel he cost about $5000). Sure it's a tiny job for them, but I doubt it would be cheap. You could do it yourself and overkill the job with a few posts and large beams.

I have an accessible crawl space, around 3-4 feet tall there. Plastic vapor barrier over dirt. The tank will be next to the wall to the garage, which goes to concrete slab for the garage. Unfortunately the 2x6" joists under the tank every 16" run parallel to that wall and to the tank. There are 2 joists running under where the tank will be.

My contractor proposes sistering the two existing 2x6" joists each with two 2x12" joists plus 1 sistered to the joist along the wall (5 new 2x12" joists total). Then running 2 girder beams under the sistered joists, 1 on each side of the length of the tank. Then support the girder beams with two 4x6" posts to new concrete piers.

It seems like a reasonable plan to me but will be expensive because of labor, estimate is $2300. The price tag is what made me take a step back and wonder if he is over-building it and if a structural engineer's report could allow for a more modest and affordable approach. But if the SE is expensive too, it probably wouldn't help things.

I don't doubt that some of you are very handy and wouldn't have a problem DIY'ing this. But my lack of experience, free time, helper, and interest in working under the house make it out of the question for me.

He probably is overbuilding it to some degree, but in the absence of a structural engineer saying that less is needed, I would overbuild it too. To get a structural engineer to assess the structure would likely end up costing you more money. So besides getting more quotes, you're probably stuck.

Yea, structural engineer would cost you hundreds maybe even over a thousand more for a small project like yours. We removed a load bearing wall and put in a large cross beam in the ceiling, SE cost $1500. We used Efe from 4x Engineering, but we're in the South Bay. I'm sure others will chime in with possibly DIY info. I would definitely get more quotes for the project though.

Just get 4 of these concrete post blocks
and 4 of these jackposts
and put 2 of them under each of the 2 floor joists. Less than $200 total and less than 1 hour. You could probably even get a local handyman to do it for less than $100

The nice thing about using the jacks is you can use them even after putting water in as long as it doesn't completely fail. What I've done in the past in a similar situation is to measure up onto the joist and mark a line. It doesn't matter what the measurement is it's just to use as a reference to see how much deflection is occurring. Make sure to use a rock or something on the ground under where you are measuring that will not move over the course of your measuring. Measure it with nothing there then place the tank and perhaps 1/4 of the water and measure again. I would trust up to about 1/4" of deflection beyond that and I'd want to reinforce it. In which case you can then use the concrete blocks and jacks and jack it back up to where it was before any weight was put on it.

I do think the contractor is over engineering it but $2300 for what he's doing is not unreasonable. I'd probably charge between $1800 and $3200 depending on how accessible the area was.

My contractor came out yesterday. I expressed my concerns. We went under the house together to look at the area again. He came up with another (less extensive) option of not sistering the otherwise fine looking 2x6" joists, instead having the 2 girder beams directly under the tank, spanning from mounted to the load-bearing wall across 3 joists to 2 posts (1 each beam) anchored in poured concrete footings. He didn't like the idea of using the free-standing pre-made concrete blocks, he said they aren't nearly as durable and stable as reinforced poured concrete and tend to break apart with load-shifting. Will use all earthquake-resistant mounting hardware.

I haven't gotten the new estimate yet but this seems like a safe approach that should be a bit easier to implement.